Cytokines are soluble proteins secreted by a variety of cells including monocytes or lymphocytes that regulate immune responses. Chemokines are a superfamily of chemoattractant proteins. Chemokines regulate a variety of biological responses and they promote the recruitment of multiple lineages of leukocytes and lymphocytes to a body organ tissue. Chemokines may be classified into two families according to the relative position of the first two cysteine residues in the protein. In one family, the first two cysteines are separated by one amino acid residue, the CXC chemokines, and in the other family the first two cysteines are adjacent, the CC chemokines. Two minor subgroups contain only one of the two cysteines (C) or have three amino acids between the cysteines (CX3C). In humans, the genes of the CXC chemokines are clustered on chromosome 4 (with the exception of SDF-1 gene, which has been localized to chromosome 10) and those of the CC chemokines on chromosome 17.
The molecular targets for chemokines are cell surface receptors. One such receptor is CXC chemokine receptor 4 CXCR4), which is a 7 transmembrane protein, coupled to G1 and was previously called LESTR (Loetscher, M., Geiser, T., O'Reilly, T., Zwahlen, R., Baggionlini, M., and Moser, B., (1994) J. Biol. Chem, 269, 232-237), HUMSTR (Federsppiel, B., Duncan, A. M. V., Delaney, A., Schappert, K., Clark-Lewis, I., and Jirik, F. R. (1993) Genomics 16, 707-712) and Fusin (Feng, Y., Broeder, C. C., Kennedy, P. E., and Berger, E. A. (1996) HIV-1 entry cofactor: Functional cDNA cloning of a seven-transmembrane G protein-coupled receptor, Science 272, 872-877). CXCR4 is widely expressed on cells of hemopoietic origin, and is a major co-receptor with CD4+ for human immunodeficiency virus 1 (HIV-1)(Feng, Y., Broeder, C. C., Kennedy, P. E., and Berger, E. A. (1996) HIV-1 entry cofactor: Functional cDNA cloning of a seven-transmembrane G protein-coupled receptor, Science 272, 872-877).
Currently, the only known natural ligand for CXCR4 is stromal cell derived factor one (SDF-1). Stromal cell derived factor-1α (SDF-1α) (SEQ ID NO: 6) and stromal cell derived factor-1β (SDF-1β) (SEQ ID NO: 7) are closely related members (together referred to herein as SDF-1). The native amino acid sequences of SDF-1α and SDF-1β are known, as are the genomic sequences encoding these proteins (U.S. Pat. No. 5,563,048 issued 8 Oct. 1996, and U.S. Pat. No. 5,756,084 issued 26 May 1998).
SDF-1 is functionally distinct from other chemokines in that it is reported to have a fundamental role in the trafficking, export and homing of bone marrow progenitor cells (Aiuti, A., Webb, I. J., Bleul, C., Springer, T., and Guierrez-Ramos, J. C., (1996) J. Exp. Med. 185, 111-120 and Nagasawa, T., Hirota, S., Tachibana, K., Takakura N., Nishikawa, S.-I., Kitamura, Y., Yoshida, N., Kikutani, H., and Kishimoto, T., (1996) Nature 382, 635-638). SDF-1 is also structurally distinct in that it has only about 22% amino acid sequence identity with other CXC chemokines (Bleul, C. C., Fuhlbrigge, R. C., Casasnovas, J. M., Aiuti, A., and Springer, T. A., (1996) J. Exp. Med. 184, 1101-1109). SDF-1 appears to be produced constitutively by several cell types, and particularly high levels are found in bone-marrow stromal cells (Shirozu, M., Nakano, T., Inazawa, J., Tashiro, K., Tada, H. Shinohara, T., and Honjo, T., (1995) Genomics, 28, 495-500 and Bleul, C. C., Fuhlbrigge, R. C., Casasnovas, J. M., Aiuti, A., and Springer, T. A., (1996) J. Exp. Med. 184, 1101-1109). A basic physiological role for SDF-1 is implied by the high level of conservation of the SDF-1 sequence between species. In vitro, SDF-1 stimulates chemotaxis of a wide range of cells including monocytes and bone marrow derived progenitor cells (Aiuti, A., Webb, I. J., Bleul, C., Springer, T., and Guierrez-Ramos, J. C., (1996) J. Exp. Med. 185, 111-120 and Bleul, C. C., Fuhlbrigge, R. C., Casasnovas, J. M., Aiuti, A., and Springer, T. A., (1996) J. Exp. Med. 184, 1101-1109). Particularly notable is its ability to stimulate a high percentage of resting and activated T-lymphocytes (Bleul, C. C., Fuhlbrigge, R. C., Casasnovas, J. M., Aiuti, A., and Springer, T. A., (1996) J. Exp. Med. 184, 1101-1109 and Campbell, J. J., Hendrick, J., Zlotnik, A., Siani, M. A., Thompson, D. A., and Butcher, E. C., (1998) Science, 279 381-383).
The 3-dimensional crystallographic structure of SDF-1 has been described (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007). Structure-activity analysis of SDF-1 (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007) and indicates that although N-terminal residues 1-8 or 1-9 are involved in receptor binding, the 1-8 and 1-9 peptides alone exhibited no in vitro activity indicative of receptor binding, supporting a reported conclusion that the peptides do not assume the conformation necessary for binding to the receptor. This result was taken to imply that the remainder of the protein scaffold, and/or various consensus receptor binding sites elsewhere in the protein are important for mediating the conformational requirements for N-terminal binding to the receptor (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007). Based on these results, a two-site model has been proposed for SDF-1 binding to CXCR4, involving two binding sites in residues 1-17, an N-terminal site and an upstream RFFESH site (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007). The two putative binding sites have been characterised by the sequence: KPVSLSYR-CPC-RFFESH (SEQ ID NO: 1), in which the two putative binding sites are joined by the CXC motif that characterises the whole CXC chemokine family (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007). These two putative binding regions have been identified as being important in other CC and CXC chemokines (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007 and Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007). This is consistent with the finding that although N-terminal regions of a wide variety of chemokines are critical for receptor, activation, N-terminal peptides of chemokines other than SDF-1 have been reported to lack receptor binding activity and not to be receptor agonists (Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007 and Crump, M., Gong J.-H., Loetscher, P., Rajarathnam, K., Amara, A., Arenzana-Seisdedos, F., Virelizier, J.-L., Baggiolini, M., Sykes, B. D., and Clark-Lewis, I., (1997) EMBO J., 16, 6996-7007).
Consistent with the fact that CXCR4 is a major co-receptor for HIV-1, SDF-1 blocks HIV-1 entry into CD4+ cells Oberlin, E., Amara, A., Bachelerie, F., Bessia, C., Virelizier, J.-L., Arenzana-Seisdedos, F., Schwartz, O., Heard, J.-M., Clark-Lewis, I., Legler, D. F., Loetscher, M., Baggiolini, M., and Moser, B., (1996) Nature, 382, 833-835 and Bleul, C. C., Farzan, M., Choe, H., Parolin, C., Clark-Lewis, I., Sodroksi, J., and Springer, T. A., (1996) Nature, 382, 829-833). Efforts have been made to identify SDF-1 derived peptides that interfere selectively with HIV entry, and not with SDF-1 signalling (Heveker, N. et al., 1998, Current Biology 8(7):369-376). A wide range of potential CXCR4 binding fragments of SDF-1 have been proposed for use in blocking HIV infection (WO 9728258, published 7 Aug. 1997; WO 9804698, published 5 Feb. 1998). As these references make clear, the anti-HIV activity of SDF-1, or fragments of SDF-1, does not depend on antagonism of the CXCR4 receptor.
Interferon gamma is an important cytokine that is released by activated T-lymphocytes (T-cells) and acts as a potent immunomodulator. Interferon gamma production by T-cells in vivo may cause other cells in the body to release additional cytokines, enzymes and antibodies that are capable of modulating many aspects of an immune response. Agents which effect the ability of activated T-cells to produce interferon gamma are characterized as immunomodulators.
Autoimmune diseases are a group of illnesses generally understood to be caused by the over-production of cytokines, lymphotoxins and antibodies by white blood cells, including in particular T-cells. During an autoimmune reaction, T-cells are understood to release chemical mediators such as interferon gamma which lead to the development of pathological symptoms of autoimmune reaction. A treatment for autoimmune diseases may therefore involve the use of agents capable of inhibiting release of interferon gamma from T-cells. Such autoimmune diseases may include, for example, Multiple Sclerosis (MS), Guillain-Barre Syndrome, Amotrophic Lateral Sclerosis, Parkinson's disease, Alzheimer's disease, Gout, Lupus, and any other human illnesses that T-cells play a major role in, such as tissue graft rejection.
Interferon beta is a cytokine that has found to have therapeutic application in the treatment of a variety of autoimmune diseases. In autoimmune diseases such as MS, the activation of Th1 type T-cells is thought to be a primary component of the autoimmune response. In MS, the autoimmune response attacks the myelin sheath neuronal axons. One of the classical markers of Th1 cell activation is the production of interferon gamma. In the development of interferon beta as a therapeutic agent for the treatment of MS, studies were conducted to demonstrate the ability of interferon beta to decrease the rate of production of interferon gamma from lymphocytes in vitro (Ann. Neurol. 1998; 44: 27-34 and Neurology 1998; 50: 1294-1300). The reduction of interferon gamma release by treatment with interferon beta is an indication of the effectiveness of interferon beta in the treatment of MS. There is a continuing need for other agents that inhibit the production of interferon gamma, particularly agents for use in the treatment of autoimmune disease, including agents that may work synergistically to enhance the effect of existing agents such as interferon beta.
Solid tumour growth is generally angiogenesis (neovascularization)-dependent, and angiogenesis inhibitors have therefore been used as agents for the treatment of solid tumours and metastasis. Endothelial cells (EC) in the vasculature play an essential role in angiogenesis, and there is accordingly a need for therapeutic agents that target this activity. The proliferation, migration and differentiation of vascular endothelial cells during angiogenesis is understood to be modulated in both normal and disease states by the complex interactions of a variety of chemokines and chemokine receptors. CXCR4 is expressed on vascular EC, and in such cells is reportedly the most abundant receptor amongst all examined chemokine receptors (Gupta, et al, 1998).